Inventing the Enemy: Essays

THE SHAPE OF THE SKY

But let us leave the Earth and look at the sky. Aristarchus of Samos had advanced a heliocentric theory between the fourth and third centuries B.C.E., as Copernicus recorded. Plutarch tells us that Aristarchus was accused of impiety precisely because he had put the Earth in movement so as to explain, through earthly rotation, astronomical phenomena that could not otherwise be accounted for. Plutarch did not agree with this theory and Ptolemy later judged it “ridiculous.” Aristarchus was way ahead of his time, and perhaps he reached his conclusion for the wrong reasons. There again, the history of astronomy is curious. A great materialist such as Epicurus developed an idea that survived for so long that it was still being discussed by Gassendi in the seventeenth century, as well as appearing in Lucretius’s De rerum natura. He suggested that the sun, the moon, and the stars (for many very serious reasons) can be neither larger nor smaller than how they appear to our senses. So Epicurus judged the sun to have a diameter of about thirty centimeters.

Copernicus’s De revolutionibus orbium coelestium was published in 1543. We imagine the world was suddenly turned upside-down and we talk about the Copernican revolution. But Galileo’s Dialogo sopra i due massimi sistemi was published in 1632 (eighty-nine years later) and we know what opposition this met. There again, the astronomies of both Copernicus and Galileo were imaginary, since they were wrong about the nature of planetary orbits.

But the most rigorous of imaginary astronomies was that of Tycho Brahe, a great astronomer and Kepler’s teacher, who admitted that planets rotate around the sun—otherwise many astronomical phenomena could not be explained—but claimed that the sun and planets rotate around the Earth, which remains immobile at the center of the universe.

Brahe’s theory was taken seriously, for example, by the Jesuits and especially by Athanasius Kircher. Kircher was a cultured man and could no longer accept the Ptolemaic system. In an illustration of solar systems in his Iter extaticum coeleste (1660 edition), alongside the Platonic system and the Egyptian system he shows us the Copernican system, explaining it accurately, but adding this note: quem deinde secuti sunt pene omnes Mathematici Acatholici et nonnulli ex Catholicis, quibus nimirum ingenium et calamus prurit ad nova venditanda. This was later accepted by almost all non-Catholic and some Catholic mathematicians, namely those who evidently had a craving to peddle new ideas in their writings. Not being of that accursed breed, Kircher thus prefers Brahe.

There were, however, very strong arguments against the idea of an Earth that moves around the sun. In his Utriusque cosmi historia of 1617, Robert Fludd uses mechanical arguments to show that if you have to turn a wheel, like that of the celestial wheel, it is easier to make it turn by exercising a force around the circumference—the point among the spheres where the primum mobile was—than by acting on the center, where the foolish Copernicans would place the sun and every generating force of life and motion. Alessandro Tassoni, in his Dieci libri di pensieri diversi of 1627, lists a range of reasons why the movement of the Earth seemed inconceivable. I will quote two of them.

Argument of the Eclipse. By removing the Earth from the center of the universe, it has to be placed either below or above the moon. If we place it below, there will never be an eclipse of the sun since the moon, being above the sun and above the Earth, will never come between the Earth and the sun. If we place it above, there will never be an eclipse of the moon, since the Earth will never be able to come between it and the sun. And what is more, astronomy could no longer predict eclipses, since it bases its calculations on the movements of the sun, and if the sun does not move, such calculations would be in vain.

Argument of the Birds. If the Earth moves, birds flying westward would never be able to keep up with its rotation and would never go forward.

Descartes, who favored Galileo’s hypothesis but never had the courage to publish his opinions about it, had developed quite an interesting theory involving vortexes, or tourbillons, in Principia philosophiae (1644). He imagined that the heavens were liquid matter, like a sea, swirling about, forming eddies or whirlpools. These vortexes carry planets with them, and the Earth is carried in a vortex around the sun. But it is the vortex that moves. The Earth remains immobile in the vortex that carries it. Descartes was shrewd in setting out these astonishing explanations—a way of getting out of the impasse between the geocentric and heliocentric arguments—as a mere hypothesis, without having to dispute the truth recognized by the church.

As Apollinaire said, Pitié, pitié pour nous qui combattons aux frontières de l’illimité et de l’avenir, pitié pour nos péchés, pitié pour nos erreurs . . . These were times when the astronomer could still commit many serious mistakes, as happened to Galileo when, through his telescope, he discovered the rings of Saturn but could not work out what they were.

First of all he declares he has seen not one single star but three joined together in a straight line parallel to the equinoctial, and represents what he has seen as three small circles. In his later writing he suggests that Saturn may appear in the shape of an olive, and finally he no longer describes three bodies or an olive, but “two semi-ellipses with two very dark little triangles in the middle of the said figures” and draws Saturn to look very much like Mickey Mouse.

Only later would Huygens describe a ring.